This disclosure relates generally to methods and apparatus for centralizing an expandable tubular member within a wellbore. More specifically, this disclosure relates to methods and apparatus for centralizing an expandable tubular member within a wellbore with a centralizer that includes collars with a frangible region.
Centralizers are used to maintain a radial stand-off between a wellbore tubular, such as a casing, and the interior wall of the wellbore in which the tubular is being installed. Maintaining this radial stand-off can help to reduce the likelihood of the wellbore tubular becoming stuck during running and provides a suitable annulus for cementing the tubular into the wellbore.
One type of centralizer is a bow spring centralizer that utilizes a plurality of flexible bow springs distributed around the circumference of the wellbore tubular. Bow spring centralizers generally include a pair of axially-spaced collars that surround the wellbore tubular and are coupled together by the plurality of bow springs. The bow springs are arranged to bow radially outwardly from the axis of the wellbore tubular so as to engage the wall of the wellbore. Thus, the bow springs provide stand-off from the wall of the wellbore and can flex, or collapse, inwardly in order to accommodate restrictions in the wellbore.
Expandable tubular are used in certain applications where wellbore restrictions may limit the diameter of a tubular that can be used. Expandable tubulars are run into the wellbore and then radially expanded to a larger diameter by any number of processes. Conventional centralizers are likely to interfere with, or be damaged during, the expansion process and often are not used with expandable tubular systems.
Thus, there is a continuing need in the art for methods and apparatus for centralizing expandable tubulars.